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Title: Application of In-Situ High Energy-Resolution Fluorescence Detection and Time-Resolved X-Ray Spectroscopy: Catalytic Activation of Oxygen over Supported Gold Catalysts

Abstract

Life-time-broadening reduction in high-energy-resolution fluorescence detected XAS produced spectra of unprecedented detail. Au L3 edge spectra of a Au/Al2O3 catalyst under various reaction conditions showed the interaction of oxygen with the gold particles on this catalyst. A reaction path on the gold particle in the oxidation of CO was established.

Authors:
 [1];  [2]; ;  [3]
  1. Institute for Chemical and Bioengineering, ETH Zurich (Switzerland)
  2. University of Southampton, School of Chemistry, Southampton (United Kingdom)
  3. European Synchrotron Radiation Facility, Grenoble (France)
Publication Date:
OSTI Identifier:
21054709
Resource Type:
Journal Article
Resource Relation:
Journal Name: AIP Conference Proceedings; Journal Volume: 882; Journal Issue: 1; Conference: XAFS13: 13. international conference on X-ray absorption fine structure, Stanford, CA (United States), 9-14 Jul 2006; Other Information: DOI: 10.1063/1.2644621; (c) 2007 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; ABSORPTION SPECTROSCOPY; ALUMINIUM OXIDES; CARBON MONOXIDE; CATALYSTS; ENERGY RESOLUTION; FLUORESCENCE; GOLD; INTERFACES; OXIDATION; OXYGEN; PARTICLES; REDUCTION; TIME RESOLUTION; X-RAY SPECTRA; X-RAY SPECTROSCOPY

Citation Formats

Bokhoven, Jeroen A. van, Tromp, Moniek, Glatzel, Pieter, and Safonova, Olga. Application of In-Situ High Energy-Resolution Fluorescence Detection and Time-Resolved X-Ray Spectroscopy: Catalytic Activation of Oxygen over Supported Gold Catalysts. United States: N. p., 2007. Web. doi:10.1063/1.2644621.
Bokhoven, Jeroen A. van, Tromp, Moniek, Glatzel, Pieter, & Safonova, Olga. Application of In-Situ High Energy-Resolution Fluorescence Detection and Time-Resolved X-Ray Spectroscopy: Catalytic Activation of Oxygen over Supported Gold Catalysts. United States. doi:10.1063/1.2644621.
Bokhoven, Jeroen A. van, Tromp, Moniek, Glatzel, Pieter, and Safonova, Olga. Fri . "Application of In-Situ High Energy-Resolution Fluorescence Detection and Time-Resolved X-Ray Spectroscopy: Catalytic Activation of Oxygen over Supported Gold Catalysts". United States. doi:10.1063/1.2644621.
@article{osti_21054709,
title = {Application of In-Situ High Energy-Resolution Fluorescence Detection and Time-Resolved X-Ray Spectroscopy: Catalytic Activation of Oxygen over Supported Gold Catalysts},
author = {Bokhoven, Jeroen A. van and Tromp, Moniek and Glatzel, Pieter and Safonova, Olga},
abstractNote = {Life-time-broadening reduction in high-energy-resolution fluorescence detected XAS produced spectra of unprecedented detail. Au L3 edge spectra of a Au/Al2O3 catalyst under various reaction conditions showed the interaction of oxygen with the gold particles on this catalyst. A reaction path on the gold particle in the oxidation of CO was established.},
doi = {10.1063/1.2644621},
journal = {AIP Conference Proceedings},
number = 1,
volume = 882,
place = {United States},
year = {Fri Feb 02 00:00:00 EST 2007},
month = {Fri Feb 02 00:00:00 EST 2007}
}
  • High energy resolution fluorescence detection (HERFD) X-ray adsorption spectroscopy (XAS) is demonstrated as a new tool to identify the geometry of metal adsorption sites and the orbitals involved in bonding. The type of CO adsorption site on a nanoparticular Pt-Al2O3 catalyst is determined. The orbitals involved in the Pt - CO bonding are identified using theoretical FEFF8.0 calculations. In situ application of HERFD XAS is applicable to a large number of catalytic systems and will provide fundamental insights in structure - performance relationships.
  • The merits of employing the energy-dispersive mode for recording the dynamics of the structural changes accompanying the thermal activation of an as-prepared catalyst are illustrated by a time-resolved investigation of the dehydration of an Ni{sup 2+}-exchanged Na{sup +} zeolite Y catalyst (see Couves, Jones, Thomas, and Smith, Adv. Mater. 1990, 2, 181). EXAFS data for a model metallic nickel catalyst, collected in 500 ms, are also shown. These yield quantitatively reliable structural information, thus demonstrating the feasibility of conducting routine, dynamic studies of heterogeneous catalysts and a variety of other material under operating conditions.
  • Desulfation by hydrogen of pre-sulfated Pt(2wt%) BaO(20wt%)/Al2O3 with various sulfur loading (S/Ba = 0.12, 0.31 and 0.62) were investigated by combining H2 temperature programmed reaction (TPRX), x-ray photoelectron spectroscopy (XPS), in-situ sulfur K-edge x-ray absorption near-edge spectroscopy (XANES), and synchrotron time-resolved x-ray diffraction (TR-XRD) techniques. We find that the amount of H2S desorbed during the desulfation in the H2 TPRX experiments is not proportional to the amount of initial sulfur loading. The results of both in-situ sulfur K-edge XANES and TR-XRD show that at low sulfur loadings, sulfates were transformed to a BaS phase and remained in the catalyst, rathermore » than being removed as H2S. On the other hand, when the deposited sulfur level exceeded a certain threshold (at least S/Ba = 0.31) sulfates were reduced to form H2S, and the relative amount of the residual sulfide species in the catalyst was much less than at low sulfur loading. Unlike samples with high sulfur loading (e.g., S/Ba = 0.62), H2O did not promote the desulfation for the sample with S/Ba of 0.12, implying that the formed BaS species originating from the reduction of sulfates at low sulfur loading are more stable to hydrolysis. The results of this combined spectroscopy investigation provide clear evidence to show that sulfates at low sulfur loadings are less likely to be removed as H2S and have a greater tendency to be transformed to BaS on the material, leading to the conclusion that desulfation behavior of Pt BaO/Al2O3 lean NOx trap catalysts is markedly dependent on the sulfation levels.« less
  • Desulfation by hydrogen of presulfated Pt (2 wt %)-BaO(20 wt %)/Al{sub 2}O{sub 3} with various sulfur loading (S/Ba = 0.12, 0.31, and 0.62) were investigated by combining H{sub 2} temperature programmed reaction (TPRX), X-ray photoelectron spectroscopy (XPS), in situ sulfur K-edge X-ray absorption near-edge spectroscopy (XANES), and synchrotron time-resolved X-ray diffraction (TR-XRD) techniques. We find that the amount of H{sub 2}S desorbed during the desulfation in the H{sub 2} TPRX experiments is not proportional to the amount of initial sulfur loading. The results of both in situ sulfur K-edge XANES and TR-XRD show that at low sulfur loadings, sulfates weremore » transformed to a BaS phase and remained in the catalyst rather than being removed as H{sub 2}S. On the other hand, when the deposited sulfur level exceeded a certain threshold (at least S/Ba = 0.31) sulfates were reduced to form H{sub 2}S, and the relative amount of the residual sulfide species in the catalyst was much less than at low sulfur loading. Unlike samples with high sulfur loading (e.g., S/Ba = 0.62), H{sub 2}O did not promote the desulfation for the sample with S/Ba of 0.12, implying that the formed BaS species originating from the reduction of sulfates at low sulfur loading are more stable to hydrolysis. The results of this combined spectroscopy investigation provide clear evidence to show that sulfates at low sulfur loadings are less likely to be removed as H{sub 2}S and have a greater tendency to be transformed to BaS on the material, leading to the conclusion that desulfation behavior of Pt-BaO/Al{sub 2}O{sub 3} lean NO{sub x} trap catalysts is markedly dependent on the sulfation levels.« less
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